A pressure indicator for a high-pressure accumulator system is known from European Patent Publication EP 1 219 942 A1. In this pressure indicator for hydraulic and/or pneumatic pressure systems, consisting of a housing with a pressure side which is connectable to a pressure space of the pressure system and of an opposite indicating side, and also of an indicating element guided displaceably between the pressure side and indicating side in the housing, the indicating element is pressurizable on the pressure side and is thereby displaceable counter to spring force from an inoperative position into a pressure-indicating position of the indicating side. The pressure indicator may be produced inexpensively because of the very simple design thereof and is therefore also suitable as a mass-produced product. The components are preferably held within the housing without screw connections. This is achieved on the indicating side by a flanged closure element. In addition, damping means for damping the movement of the indicating element are provided.
Pressure indicators of this type permit rapid visual discernment of the respective pressure state. In the unpressurized state, the pin-like indicating element is in the inoperative position thereof, which is brought about by spring force and in which the end surface thereof ends approximately flush with a housing on the indicating side. In the event of pressurization, the indicating element is moved counter to the spring force into the pressure-indicating position thereof, which protrudes in a visually discernible manner over the housing. Such pressure indicators are generally suitable only for relatively low pressures.
Although pressure indicators, such as the pressure indicator disclosed in European Patent Publication EP 1 219 942 A1, are fundamentally suitable for higher pressures, the pressure indicators do not have any security against excess pressure and have a limited function at low temperatures, since the sealing ring may jam the indicating element. The use of a closure element as a holding device for the sealing ring necessitates an additional component which increases the costs but reduces the security at very high pressures, since the component has to withstand the compressive force of the sealing ring.
A multiplicity of rupture screw connections for constructing containers and for valves are known in the prior art. Rupture discs are effective means of protecting against pressure losses which protect a container or a system from damaging excess pressure or under-pressure by an expendable diaphragm rupturing. Rupture discs are therefore a type of predetermined breaking point. The diaphragm is generally a thin metal foil made of steel or stainless steel. Rupture discs are frequently used in conjunction with a safety valve in order to ensure the tightness of the system protected therewith during normal operation.
Both German Patent Publication DE 1 000 197 B and German Patent Publication DE 916 140 C disclose the use of rupture discs in conjunction with indicating elements. However, in both cases, the indicating element is connected downstream of the rupture disc and is used only reliably to indicate the response of the rupture disc and therefore the rupturing thereof.
In many applications, a permissible operating pressure of a pressure accumulator container or of a high-pressure accumulator system has to be reliably maintained, in particular over the course of a filling operation, in order to prevent damage to pressure accumulator containers and pressure lines. It is frequently desirable for the operating pressure also to be indicated reliably at the same time.